A multilayer ceramic capacitor as an example of an electronic device has a capacitor element body, wherein a plurality of dielectric layers composed of a dielectric ceramic composition having a predetermined composition and a plurality of internal electrode layers including a variety of metals as its main component are alternately stacked. This kind of a multilayer ceramic capacitor is normally formed by printing a conductive paste on a green sheet made by a dielectric ceramic composition, stacking the plurality of green sheets printed with the conductive paste and firing the green sheets and internal electrode layers as one body.
In recent years, to use inexpensive base metals (for example, nickel and copper, etc.) as an internal electrode material, a variety of proposals have been made on dielectric ceramic compositions (for example, refer to the patent articles 1 to 4).
However, in any of the dielectric ceramic compositions, there were disadvantages that dielectric characteristics (capacity change, a dielectric loss) declined at a low frequency after firing or the accelerated lifetime of insulation resistance after firing became short in some cases. Therefore, when producing a multilayer ceramic capacitor having internal electrodes made by nickel or other base metal by using the dielectric ceramic composition, reliability of a multilayer ceramic capacitor to be obtained was liable to decline.
Thus, there have been made a variety of proposals to improve an accelerated lifetime of insulation resistance of a dielectric ceramic composition to improve reliability of a multilayer ceramic capacitor using the dielectric ceramic composition (for example, refer to the patent articles 5 to 7).
The patent article 5 discloses a dielectric ceramic composition including a dielectric oxide having a composition expressed by (Ca1-x Srx)m·(Zr1-y Tiy)O3 as a main component (note that 0.94≦m<1.08, 0≦x≦1.00 and 0.8≦y≦1.00), at least one kind of oxides of V, Nb, W, Ta and Mo by an amount of 0.01 to 2 moles (note that 2 moles is excluded), MnO2 by an amount of less than 4 moles and at least one kind of SiO2, MO (note that M is at least one kind of element selected from Ba, Ca, Sr and Mg), Li2O and B2O3 by an amount of less than 15 moles with respect to 100 moles of the main component.
The patent article 6 discloses a dielectric ceramic composition including a dielectric oxide having a composition expressed by (Ca1-x Srx)m·(Zr1-y Tiy)O3 as a main component (note that 0.75≦m≦1.04, 0≦x≦1.00 and 0≦y≦0.1), at least one kind of oxides of Nb, W, Ta and Mo except for V, Al2O3 by an amount of 0.1 to 10 moles, MnO2 by an amount of 0.2 to 5 moles, and a composite oxide of Ba, Ca, Si and O by an amount of 0.5 to 15 moles with respect to 100 moles of the main component.
The patent article 7 discloses a dielectric ceramic composition including a dielectric oxide having a composition expressed by (Ca1-x Srx)m·(Zr1-y Tiy)O3 as a main component (note that 0.8≦m≦1.3, 0≦x≦1.00 and 0.1≦y≦0.8), at least one kind of oxides of V, Nb, W, Ta and Mo by an amount of 0.01 to 5 moles, MnO2 by an amount of 0.2 to 5 moles, at least one kind of SiO2, MO (note that M is at least one kind of element selected from Ba, Ca, Sr and Mg), Li2O and B2O3 by an amount of less than 15 moles with respect to 100 moles of the main component.
However, still, a sufficient accelerated lifetime of insulation resistance may not be obtained in the dielectric ceramic compositions described in the patent articles 5 to 7. As a result, when producing a multilayer ceramic capacitor having internal electrodes made by a base metal, such as nickel, by using the dielectric ceramic composition, reliability of the multilayer ceramic capacitor cannot be improved in some cases.
Patent Article 1: The Japanese Unexamined Patent Publication No. 11-224827
Patent Article 2: The Japanese Unexamined Patent Publication No. 60-131708
Patent Article 3: The Japanese Unexamined Patent Publication No. 57-37081
Patent Article 4: The Japanese Examined Patent Publication No. 63-126117
Patent Article 5: The Japanese Unexamined Patent Publication No. 2002-80278
Patent Article 6: The Japanese Patent Publication No. 2997236
Patent Article 7: The International Patent Publication No. WO02/00568